The Tiger's Claw may have been heavily armed, but she was never meant to take on enemy capital ships by intention. Her armament was designed to reduce the number of escorts that she required in battle. Her strength was in her spacecraft complement.
I believe thatthe Confederation class dreadnought was designed to effectively fight at all ranges. A complement of spacecraft for very long range (BVR) attacks and effective close in defense. The Phase Transit Cannon and AMG battery for anti-capital ship combat. The latter, if I remember right, could also be used against attacking fighters and bombers. Point defense lasers for anti-fighter and torpedo work.
As for what was the Confederation's main weapon, I would say that it depended on the situation and range. For close quarters battle, it probably would be her PTC and AMG battery. For a strike situation like K'Tithrak Mang or Vukar Tag, her spacecraft complement would be her strength. It's all relative.